Cleaning system utilizing an organic cleaning solvent and a pressurized fluid solvent

ABSTRACT

A cleaning system that utilizes an organic cleaning solvent and pressurized fluid solvent is disclosed. The system has no conventional evaporative hot air drying cycle. Instead, the system utilizes the solubility of the organic solvent in pressurized fluid solvent as well as the physical properties of pressurized fluid solvent. After an organic solvent cleaning cycle, the solvent is extracted from the textiles at high speed in a rotating drum in the same way conventional solvents are extracted from textiles in conventional evaporative hot air dry cleaning machines. Instead of proceeding to a conventional drying cycle, the extracted textiles are then immersed in pressurized fluid solvent to extract the residual organic solvent from the textiles. This is possible because the organic solvent is soluble in pressurized fluid solvent. After the textiles are immersed in pressurized fluid solvent, pressurized fluid solvent is pumped from the drum. Finally, the drum is de-pressurized to atmospheric pressure to evaporate any remaining pressurized fluid solvent, yielding clean, solvent free textiles. The organic solvent is preferably dipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether or tripropylene glycol methyl ether, a mixture thereof, or a similar solvent and the pressurized fluid solvent is preferably densified carbon dioxide.

BACKGROUND

[0001] 1. Field of the Invention

[0002] The present invention relates generally to cleaning systems, andmore specifically to substrate cleaning systems, such as textilecleaning systems, utilizing an organic cleaning solvent and apressurized fluid solvent.

[0003] 2. Related Art

[0004] A variety of methods and systems are known for cleaningsubstrates such as textiles, as well as other flexible, precision,delicate, or porous structures that are sensitive to soluble andinsoluble contaminants. These known methods and systems typically usewater, perchloroethylene, petroleum, and other solvents that are liquidat or substantially near atmospheric pressure and room temperature forcleaning the substrate.

[0005] Such conventional methods and systems generally have beenconsidered satisfactory for their intended purpose. Recently, however,the desirability of employing these conventional methods and systems hasbeen questioned due to environmental, hygienic, occupational hazard, andwaste disposal concerns, among other things. For example,perchloroethylene frequently is used as a solvent to clean delicatesubstrates, such as textiles, in a process referred to as “drycleaning.” Some locales require that the use and disposal of thissolvent be regulated by environmental agencies, even when only traceamounts of this solvent are to be introduced into waste streams.

[0006] Furthermore, there are significant regulatory burdens placed onsolvents such as perchloroethylene by agencies such as the EPA, OSHA andDOT. Such regulation results in increased costs to the user, which, inturn, are passed to the ultimate consumer. For example, filters thathave been used in conventional perchloroethylene dry cleaning systemsmust be disposed of in accordance with hazardous waste or otherenvironmental regulations. Certain other solvents used in dry cleaning,such as hydrocarbon solvents, are extremely flammable, resulting ingreater occupational hazards to the user and increased costs to controltheir use.

[0007] In addition, textiles that have been cleaned using conventionalcleaning methods are typically dried by circulating hot air through thetextiles as they are tumbled in a drum. The solvent must have arelatively high vapor pressure and low boiling point to be usedeffectively in a system utilizing hot air drying. The heat used indrying may permanently set some stains in the textiles. Furthermore, thedrying cycle adds significant time to the overall processing time.During the conventional drying process, moisture adsorbed on the textilefibers is often removed in addition to the solvent. This often resultsin the development of undesirable static electricity and shrinkage inthe garments. Also, the textiles are subject to greater wear due to theneed to tumble the textiles in hot air for a relatively long time.Conventional drying methods are inefficient and often leave excessresidual solvent in the textiles, particularly in heavy textiles,components constructed of multiple fabric layers, and structuralcomponents of garments such as shoulder pads. This may result inunpleasant odors and, in extreme cases, may cause irritation to the skinof the wearer. In addition to being time consuming and of limitedefficiency, conventional drying results in significant loss of cleaningsolvent in the form of fugitive solvent vapor. Finally, conventional hotair drying is an energy intensive process that results in relativelyhigh utility costs and accelerated equipment wear.

[0008] Traditional cleaning systems may utilize distillation inconjunction with filtration and adsorption to remove soils dissolved andsuspended in the cleaning solvent. The filters and adsorptive materialsbecome saturated with solvent, therefore, disposal of some filter wasteis regulated by state or federal laws. Solvent evaporation especiallyduring the drying cycle is one of the main sources of solvent loss inconventional systems. Reducing solvent loss improves the environmentaland economic aspects of cleaning substrates using cleaning solvents. Itis therefore advantageous to provide a method and system for cleaningsubstrates that utilize a solvent having less adverse attributes thanthose solvents currently used and reduces solvent losses.

[0009] As an alternative to conventional cleaning solvents, pressurizedfluid solvents or densified fluid solvents have been used for cleaningvarious substrates, wherein densified fluids are widely understood toencompass gases that are pressurized to either subcritical orsupercritical conditions so as to achieve a liquid or a supercriticalfluid having a density approaching that of a liquid. In particular, somepatents have disclosed the use of a solvent such as carbon dioxide thatis maintained in a liquid state or either a subcritical or supercriticalcondition for cleaning such substrates as textiles, as well as otherflexible, precision, delicate, or porous structures that are sensitiveto soluble and insoluble contaminants.

[0010] For example, U.S. Pat. No. 5,279,615 discloses a process forcleaning textiles using densified carbon dioxide in combination with anon-polar cleaning adjunct. The preferred adjuncts are paraffin oilssuch as mineral oil or petrolatum. These substances are a mixture ofalkanes including a portion of which are C₁₆ or higher hydrocarbons. Theprocess uses a heterogeneous cleaning system formed by the combinationof the adjunct which is applied to the textile prior to or substantiallyat the same time as the application of the densified fluid. According tothe data disclosed in U.S. Pat. No. 5,279,615, the cleaning adjunct isnot as effective at removing soil from fabric as conventional cleaningsolvents or as the solvents described for use in the present inventionas disclosed below.

[0011] U.S. Pat. No. 5,316,591 discloses a process for cleaningsubstrates using liquid carbon dioxide or other liquefied gases belowtheir critical temperature. The focus of this patent is on the use ofany one of a number of means to effect cavitation to enhance thecleaning performance of the liquid carbon dioxide. In all of thedisclosed embodiments, densified carbon dioxide is the cleaning medium.This patent does not describe the use of a solvent other than theliquefied gas for cleaning substrates. While the combination ofultrasonic cavitation and liquid carbon dioxide may be well suited toprocessing complex hardware and substrates containing extremelyhazardous contaminants, this process is too costly for the regularcleaning of textile substrates. Furthermore, the use of ultrasoniccavitation is less effective for removing contaminants from textilesthan it is for removing contaminants from hard surfaces.

[0012] U.S. Pat. No. 5,377,705 discloses a process for cleaningprecision parts utilizing a liquefied pressurized gas in thesupercritical state and an environmentally acceptable co-solvent. Duringthis process, the parts to be cleaned are pre-treated with theco-solvent and then placed in the cleaning vessel. Afterwards, thecontaminants and co-solvent are removed from the parts by circulating apressurized gas in its supercritical state through the vessel.Redeposition of co-solvent and contaminants is controlled by the amountof pressurized gas that is pumped through the vessel. Co-solventsspecified for use in conjunction with the cleaning solvent includealiphatics, terpenes, acetone, laminines, isopropyl alcohol, Axarel(DuPont), Petroferm (Petroferm, Inc.), kerosene, and Isopar-m (Exxon).During the cleaning process, the cleaning solvent (supercritical carbondioxide) flows through a vessel containing the parts to be treated,through a filter or filters and directly to a separator in which thesolvent is evaporated and recondensed. The disclosed co-solvents for usein this patent have high evaporation rates and low flash points. The useof such co-solvents results in high solvent losses, and high fire risks.Furthermore, many of the co-solvents are not compatible with common dyesand fibers used in textile manufacture. Also, the use of supercriticalcarbon dioxide necessitates the use of more expensive equipment.

[0013] U.S. Pat. No. 5,417,768 discloses a process for precision partscleaning using a two-solvent system. One solvent can be liquid at roomtemperature and pressure while the second solvent can be supercriticalcarbon dioxide. The objectives of this invention include using two ormore solvents with minimal mixing of the solvents and to incorporateultrasonic cavitation in such a way as to prevent the ultrasonictransducers from coming in contact with the first-mentioned solvent. Anapparatus is described which consists of an open top vessel within acovered pressurized vessel. The primary fluid is pumped into the opentop vessel. After cleaning with the primary fluid, it is pumped from theopen top vessel. Pressurized carbon dioxide is then pumped into the opentop vessel and flushed through the vessel until the level ofcontaminants within the vessel are reduced to the desired level. Theco-solvents disclosed in this patent are the same solvents specified inU.S. Pat. No. 5,377,705. Use of these solvents would introduce a highrisk of fire, high levels of solvent loss and potential damage to a widerange of textiles.

[0014] U.S. Pat. No. 5,888,250 discloses the use of a binary azeotropecomprised of propylene glycol tertiary butyl ether and water as anenvironmentally attractive replacement for perchlorethylene in drycleaning and degreasing processes. While the use of propylene glycoltertiary butyl ether is attractive from an environmental regulatorypoint of view, its use as disclosed in this invention is in aconventional dry cleaning process using conventional dry cleaningequipment and a conventional evaporative hot air drying cycle. As aresult, it has many of the same disadvantages as conventional drycleaning processes described above.

[0015] Several of the pressurized fluid solvent cleaning methodsdescribed in the above patents may lead to recontamination of thesubstrate and degradation of efficiency because the contaminated solventis not continuously purified or removed from the system. Furthermore,pressurized fluid solvent alone is not as effective at removing sometypes of soil as are conventional cleaning solvents. Consequently,pressurized fluid solvent cleaning methods require individual treatmentof stains and heavily soiled areas of textiles, which is alabor-intensive process. Furthermore, systems that utilize pressurizedfluid solvents for cleaning are more expensive and complex tomanufacture and maintain than conventional cleaning systems. Finally,few if any conventional surfactants can be used effectively inpressurized fluid solvents. The surfactants and additives that can beused in pressurized fluid solvent cleaning systems are much moreexpensive than those used in conventional cleaning systems.

[0016] There thus remains a need for an efficient and economic methodand system for cleaning substrates that incorporates the benefits ofprior systems, and minimizes the difficulties encountered with each.There also remains a need for a method and system in which the hot airdrying time is eliminated, or at least reduced, thereby reducing thewear on the substrate and preventing stains from being permanently seton the substrate.

SUMMARY

[0017] In the present invention, certain types of organic solvents, suchas glycol ethers and, specifically, poly glycol ethers includingdipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether ortripropylene glycol methyl ether, or similar solvents or mixtures ofsuch solvents are used. Any type of organic solvent that falls withinthe range of properties disclosed hereinafter may be used. However,unlike conventional cleaning systems, in the present invention, aconventional drying cycle is not necessary. Instead, the system utilizesthe solubility of the organic solvent in pressurized fluid solvents, aswell as the physical properties of pressurized fluid solvents, to drythe substrate being cleaned.

[0018] As used herein, the term “pressurized fluid solvent” refers toboth pressurized liquid solvents and densified fluid solvents. The term“pressurized liquid solvent” as used herein refers to solvents that areliquid at between approximately 600 and 1050 pounds per square inch andbetween approximately 5 and 30 degrees Celsius, but are gas atatmospheric pressure and room temperature. The term “densified fluidsolvent” as used herein refers to a gas or gas mixture that iscompressed to either subcritical or supercritical conditions so as toachieve either a liquid or a supercritical fluid having densityapproaching that of a liquid. Preferably, the pressurized fluid solventused in the present invention is an inorganic substance such as carbondioxide, xenon, nitrous oxide, or sulfur hexafluoride. Most preferably,the pressurized fluid solvent is densified carbon dioxide.

[0019] The substrates are cleaned in a perforated drum within a vesselin a cleaning cycle using an organic solvent. A perforated drum ispreferred to allow for free interchange of solvent between the drum andvessel as well as to transport soil from the substrates to the filter.After substrates have been cleaned in the perforated drum, the organicsolvent is extracted from the substrates by rotating the cleaning drumat high speed within the cleaning vessel in the same way conventionalsolvents are extracted from substrates in conventional cleaningmachines. However, instead of proceeding to a conventional evaporativehot air drying cycle, the substrates are immersed in pressurized fluidsolvent to extract the residual organic solvent from the substrates.This is possible because the organic solvent is soluble in thepressurized fluid solvent. After the substrates are immersed inpressurized fluid solvent, which may also serve as a cleaning solvent,the pressurized fluid solvent is transferred from the drum. Finally, thevessel is de-pressurized to atmospheric pressure to evaporate anyremaining pressurized fluid solvent, yielding clean, solvent-freesubstrates.

[0020] Glycol ethers, specifically poly glycol ethers, used in thepresent invention tend to be soluble in pressurized fluid solvents suchas supercritical or subcritical carbon dioxide so that a conventionalhot air drying cycle is not necessary. The types of poly glycol ethersused in conventional cleaning systems must have a reasonably high vaporpressure and a low boiling point because they must be removed from thesubstrates by evaporation in a stream of hot air. However, solvents,particularly non-halogenated solvents, that have a high vapor pressureand a low boiling point generally also have a low flash point. From asafety standpoint, organic solvents used in cleaning substrates shouldhave a flash point that is as high as possible, or preferably, it shouldhave no flash point. By eliminating the conventional hot air evaporativedrying process, a wide range of solvents can be used in the presentinvention that have much lower evaporation rates, higher boiling pointsand higher flash points than those used in conventional cleaningsystems.

[0021] Thus, the cleaning system described herein utilizes solvents thatare less regulated and less combustible, and that efficiently removedifferent soil types typically deposited on textiles through normal use.The cleaning system reduces solvent consumption and waste generation ascompared to conventional dry cleaning systems. Machine and operatingcosts are reduced as compared to currently used pressurized fluidsolvent systems, and conventional additives may be used in the cleaningsystem.

[0022] Furthermore, one of the main sources of solvent loss fromconventional dry cleaning systems, which occurs in the evaporative hotair drying step, is substantially reduced or eliminated altogether.Because the conventional evaporative hot air drying process iseliminated, there are no heat set stains on the substrates, risk of fireand/or explosion is reduced, the cleaning cycle time is reduced, andresidual solvent in the substrates is substantially reduced oreliminated. Substrates are also subject to less wear, less staticelectricity build-up and less shrinkage because there is no need totumble the substrates in a stream of hot air to dry them.

[0023] While systems according to the present invention utilizingpressurized fluid solvent to remove organic solvent can be constructedas wholly new systems, existing conventional solvent systems can also beconverted to utilize the present invention. An existing conventionalsolvent system can be used to clean substrates with organic solvent, andan additional pressurized chamber for drying substrates with pressurizedfluid solvent can be added to the existing system.

[0024] Therefore, according to the present invention, textiles arecleaned by placing the textiles to be cleaned into a cleaning drumwithin a cleaning vessel, adding an organic solvent to the cleaningvessel, cleaning the textiles with the organic solvent, removing aportion of the organic solvent from the cleaning vessel, rotating thecleaning drum to extract a portion of the organic solvent from thetextiles, placing the textiles into a drying drum within a pressurizabledrying vessel, adding a pressurized fluid solvent to the drying vessel,removing a portion of the pressurized fluid solvent from the dryingvessel, rotating the drying drum to extract a portion of the pressurizedfluid solvent from the textiles, depressurizing the drying vessel toremove the remainder of the pressurized fluid solvent by evaporation,and removing the textiles from the depressurized vessel.

[0025] These and other features and advantages of the invention will beapparent upon consideration of the following detailed description of thepresently preferred embodiment of the invention, taken in conjunctionwith the claims and appended drawings, as well as will be learned bypractice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is a block diagram of a cleaning system utilizing separatevessels for cleaning and drying.

[0027]FIG. 2 is a block diagram of a cleaning system utilizing a singlevessel for cleaning and drying.

DETAILED DESCRIPTION

[0028] Reference will now be made in detail to embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. The steps of each method for cleaning and drying a substratewill be described in conjunction with the detailed description of thesystem.

[0029] The methods and systems presented herein may be used for cleaninga variety of substrates. The present invention is particularly suitedfor cleaning substrates such as textiles, as well as other flexible,precision, delicate, or porous structures that are sensitive soluble aninsoluble contaminants. The term “textile” is inclusive of, but notlimited to, woven or non-woven materials, as well as articles therefrom.Textiles include, but are not limited to, fabrics, articles of clothing,protective covers, carpets, upholstery, furniture and window treatments.For purposes of explanation and illustration, and not limitation,exemplary embodiments of a system for cleaning textiles in accordancewith the invention are shown in FIGS. 1 and 2.

[0030] As noted above, the pressurized fluid solvent used in the presentinvention is either a pressurized liquid solvent or a densified fluidsolvent. Although a variety of solvents may be used, it is preferredthat an inorganic substance such as carbon dioxide, xenon, nitrousoxide, or sulfur hexafluoride, be used as the pressurized fluid solvent.For cost and environmental reasons, liquid, supercritical, orsubcritical carbon dioxide is the preferred pressurized fluid solvent.

[0031] Furthermore, to maintain the pressurized fluid solvent in theappropriate fluid state, the internal temperature and pressure of thesystem must be appropriately controlled relative to the criticaltemperature and pressure of the pressurized fluid solvent. For example,the critical temperature and pressure of carbon dioxide is approximately31 degrees Celsius and approximately 73 atmospheres, respectively. Thetemperature may be established and regulated in a conventional manner,such as by using a heat exchanger in combination with a thermocouple orsimilar regulator to control temperature. Likewise, pressurization ofthe system may be performed using a pressure regulator and a pump and/orcompressor in combination with a pressure gauge. These components areconventional and are not shown in FIGS. 1 and 2 as placement andoperation of these components are known in the art.

[0032] The system temperature and pressure may be monitored andcontrolled either manually, or by a conventional automated controller(which may include, for example, an appropriately programmed computer orappropriately constructed microchip) that receives signals from thethermocouple and pressure gauge, and then sends corresponding signals tothe heat exchanger and pump and/or compressor, respectively. Unlessotherwise noted, the temperature and pressure is appropriatelymaintained throughout the system during operation. As such, elementscontained within the system are constructed of sufficient size andmaterial to withstand the temperature, pressure, and flow parametersrequired for operation, and may be selected from, or designed using, anyof a variety of presently available high pressure hardware.

[0033] In the present invention, the preferred organic solvent shouldhave a flash point of greater than 200° F. to allow for increased safetyand less governmental regulation, have a low evaporation rate tominimize fugitive emissions, be able to remove soils consisting ofinsoluble particulate soils and solvent soluble oils and greases, andprevent or reduce redeposition of soil onto the textiles being cleaned.

[0034] Preferably, the organic solvent in the present invention is aglycol ether, and specifically a poly glycol ether such as dipropyleneglycol n-butyl ether, tripropylene glycol n-butyl ether or tripropyleneglycol methyl ether, or any combination of one or more of these.Additionally, any organic solvent or mixture of organic solventsexhibiting the following physical properties is suitable for use in thepresent invention: (1) soluble in carbon dioxide at a pressure ofbetween about 600 and about 1050 pounds per square inch and at atemperature of between about 5 and about 30 degrees Celsius; (2)specific gravity of greater than about 0.7 (the higher the density, thebetter the organic solvent); and (3) Hansen solubility parameters ofabout 7.2-8.1 (cal/cm³)^(1/2) for dispersion, about 2.0-4.8(cal/cm³)^(1/2) for polar, and about 4.0-7.3 (cal/cm³)^(1/2) forhydrogen bonding (based on values cited in Publication No. M-167P fromEastman Chemical Products). Preferably, in addition to the above threephysical properties, the organic solvent used in the present inventionshould also exhibit one or more of the following physical properties:(4) flash point greater than about 200 degrees Fahrenheit; and (5)evaporation rate of lower than about 30 (where n-butyl acetate=100).Most preferably, the organic solvent used in the present inventionexhibits each of the foregoing characteristics (i.e., those identifiedas (1) through (5)).

[0035] The Hansen solubility parameters were developed to characterizesolvents for the purpose of comparison. Each of the three parameters(i.e., dispersion, polar and hydrogen bonding) represents a differentcharacteristic of solvency. In combination, the three parameter are ameasure of the overall strength and selectivity of a solvent. The aboveHansen solubility parameter ranges identify solvents that are goodsolvents for a wide range of substances and also exhibit a degree ofsolubility in liquid carbon dioxide. The Total Hansen solubilityparameter, which is the square root of the sum of the squares of thethree parameters mentioned previously, provides a more generaldescription of the solvency of the organic solvents.

[0036] Dipropylene glycol n-butyl ether, tripropylene glycol n-butylether and tripropylene glycol methyl ether all fall within all of theabove parameters; however, any organic solvent or mixture of organicsolvents that meet at least properties 1 through 3, and preferably all 5properties, is suitable for use in the present invention. Furthermore,the organic solvent should also have a low toxicity and a lowenvironmental impact. Table 1 below shows the physical properties of anumber of organic solvents that may be suitable for use in the presentinvention. TABLE 1 Soluble Evaporation Hansen Solubility Parameters inSpecific Flash Rate Hydrogen carbon Gravity Point (n-butyl DispersionPolar Bonding Total Solvent dioxide (20° C./20° C.) (° F.) acetate =100) (cal/cm³)^(1/2) (cal/cm³)^(1/2) (cal/cm³)^(1/2) (cal/cm³)^(1/2)Ethylene Yes 0.931 110 30 7.9 4.5 7.0 11.5 Glycol Ethyl Ether EthyleneYes 0.973 130 20 7.8 2.3 5.2 9.7 Glycol Ethyl Ether Acetate DiethyleneYes 0.956 222 0.3 7.8 3.4 5.2 10.0 Glycol Butyl Ether Propylene Yes0.872 113 25 7.5 3.0 5.3 9.6 Glycol t-butyl (25° C./25° C.) EtherDipropylene Yes 0.951 167 2 7.6 2.8 5.5 9.8 Glycol Methyl EtherTripropylene Yes 0.962 232 0.2 7.4 3.0 5.7 9.8 Glycol Methyl EtherDipropylene Yes 0.912 214 0.4 7.4 2.2 5.5 9.5 Glycol n-Butyl EtherDipropylene Yes 0.922 190 1.3 7.4 2.4 5.7 9.6 Glycol n- Propyl EtherTripropylene Yes 0.934 255 0.029 7.4 2.4 5.1 9.3 Glycol n-Butyl Ether

[0037] In Table 1, the solvents are soluble in carbon dioxide between570 psig/5° C. and 830 psig/20° C. The flash point was measured usingTag Closed Cup for ethylene glycol ethyl ether and ethylene glycol ethylether acetate; using SETA Flash for diethylene glycol butyl ether,propylene glycol t-butyl ether, dipropylene glycol methyl ether,tripropylene glycol methyl, ether, dipropylene glycol n-butyl ether, anddipropylene glycol n-propyl ether; and using Pensky Martens Closed Cupfor tripropylene glycol n-butyl ether. The values for the evaporationrate are based on n-butyl acetate=100. Finally, the specific gravity,flash point, evaporation rate and Hansen solubility parameters wereobtained from Publication No. M-167P from Eastman Chemical Products forethylene glycol ethyl ether, ethylene glycol ethyl ether acetate,diethylene glycol butyl ether, and propyleneglycol t-butyl ether; from“Products for Cleaners and the Personal Care Industry,” Arco Chemicals(1997), for dipropylene glycol methyl ether, tripropylene glycol methylether, dipropylene glycol n-butyl ether, and dipropylene glycol n-propylether; and from Lyondell Chemical Company for tripropylene glycoln-butyl ether.

[0038] Referring now to FIG. 1, a block diagram of a cleaning systemhaving separate vessels for cleaning and drying textiles is shown. Thecleaning system 100 generally comprises a cleaning machine 102 having acleaning vessel 110 operatively connected to, via one or more motoractivated shafts (not shown), a perforated rotatable cleaning drum orwheel 112 within the cleaning vessel 110 with an inlet 114 to thecleaning vessel 110 and an outlet 116 from the cleaning vessel 110through which cleaning fluids can pass. A drying machine 104 has adrying vessel 120 capable of being pressurized. The pressurizable dryingvessel 120 is operatively connected to, via one or more motor activatedshafts (not shown), a perforated rotatable drying drum or wheel 122within the drying vessel 120 with an inlet 124 to the drying vessel 120and an outlet 126 from the drying vessel 120 through which pressurizedfluid solvent can pass. The cleaning vessel 110 and the drying vessel120 can either be parts of the same machine, or they can compriseseparate machines. Furthermore, both the cleaning and drying steps ofthis invention can be performed in the same vessel, as is described withrespect to FIG. 2 below.

[0039] An organic solvent tank 130 holds any suitable organic solvent,as previously described, to be introduced to the cleaning vessel 110through the inlet 114. A pressurized fluid solvent tank 132 holdspressurized fluid solvent to be added to the pressurizable drying vessel120 through the inlet 124. Filtration assembly 140 contains one or morefilters that continuously remove contaminants from the organic solventfrom the cleaning vessel 110 as cleaning occurs.

[0040] The components of the cleaning system 100 are connected withlines 150-156, which transfer organic solvents and vaporized andpressurized fluid solvents between components of the system. The term“line” as used herein is understood to refer to a piping network orsimilar conduit capable of conveying fluid and, for certain purposes, iscapable of being pressurized. The transfer of the organic solvents andvaporized and pressurized fluid solvents through the lines 150-156 isdirected by valves 170-176 and pumps 190-193. While pumps 190-193 areshown in the described embodiment, any method of transferring liquidand/or vapor between components can be used, such as adding pressure tothe component using a compressor to force the liquid and/or vapor fromthe component.

[0041] The textiles are cleaned with an organic solvent such as thosepreviously described or mixtures thereof. The textiles may also becleaned with a combination of organic solvent and pressurized fluidsolvent, and this combination may be in varying proportions from about50% by weight to 100% by weight of organic solvent and 0% by weight to50% by weight of pressurized fluid solvent. In the cleaning process, thetextiles are first sorted as necessary to place the textiles into groupssuitable to be cleaned together. The textiles may then be spot treatedas necessary to remove any stains that may not be removed during thecleaning process. The textiles are then placed into the cleaning drum112 of the cleaning system 100. It is preferred that the cleaning drum112 be perforated to allow for free interchange of solvent between thecleaning drum 112 and the cleaning vessel 110 as well as to transportsoil from the textiles to the filtration assembly 140.

[0042] After the textiles are placed in the cleaning drum 112, anorganic solvent contained in the organic solvent tank 130 is added tothe cleaning vessel 110 via line 152 by opening valve 171, closingvalves 170, 172, 173 and 174, and activating pump 190 to pump organicsolvent through the inlet 114 of the cleaning vessel 110. The organicsolvent may contain one or more co-solvents, water, detergents, or otheradditives to enhance the cleaning capability of the cleaning system 100.Alternatively, one or more additives may be added directly to thecleaning vessel 110. Pressurized fluid solvent may also be added to thecleaning vessel 10 along with the organic solvent to enhance cleaning.Pressurized fluid solvent can be added to the cleaning vessel 110 vialine 154 by opening valve 174, closing valves 170, 171, 172, 173, and175, and activating pump 192 to pump pressurized fluid solvent throughthe inlet 114 of the cleaning vessel 110. Of course, if pressurizedfluid solvent is included in the cleaning cycle, the cleaning vessel 110will need to be pressurized in the same manner as the drying vessel 120,as discussed below.

[0043] When a sufficient amount of the organic solvent, or combinationof organic solvent and pressurized fluid solvent, is added to thecleaning vessel 110, the motor (not shown) is activated and theperforated cleaning drum 112 is agitated and/or rotated within cleaningvessel 110. During this phase, the organic solvent is continuouslycycled through the filtration assembly 140 by opening valves 170 and172, closing valves 171, 173 and 174, and activating pump 191.Filtration assembly 140 may include one or more fine mesh filters toremove particulate contaminants from the organic solvent passingtherethrough and may alternatively or in addition include one or moreabsorptive or adsorptive filters to remove water, dyes and otherdissolved contaminants from the organic solvent. Exemplaryconfigurations for filter assemblies that can be used to removecontaminants from either the organic solvent or the pressurized fluidsolvent are described more fully in U.S. application Ser. No. 08/994,583incorporated herein by reference. As a result, the organic solvent ispumped through outlet 116, valve 172, line 151, filter assembly 140,line 150, valve 170 and re-enters the cleaning vessel 110 via inlet 114.This cycling advantageously removes contaminants, including particulatecontaminants and/or soluble contaminants, from the organic solvent andreintroduces filtered organic solvent to the cleaning vessel 110 andagitating or rotating cleaning drum 112. Through this process,contaminants are removed from the textiles. Of course, in the event thecleaning vessel 110 is pressurized, this recirculation system will bemaintained at the same pressure/temperature levels as those in cleaningvessel 110.

[0044] After sufficient time has passed so that the desired level ofcontaminants is removed from the textiles and organic solvent, theorganic solvent is removed from the cleaning drum 112 and cleaningvessel 110 by opening valve 173, closing valves 170, 171, 172 and 174,and activating pump 191 to pump the organic solvent through outlet 116via line 153. The cleaning drum 112 is then rotated at a high speed,such as 400-800 rpm, to further remove organic solvent from thetextiles. The cleaning drum 112 is preferably perforated so that, whenthe textiles are rotated in the cleaning drum 112 at a high speed, theorganic solvent can drain from the cleaning drum 112. Any organicsolvent removed from the textiles by rotating the cleaning drum 112 athigh speed is also removed from the cleaning drum 112 in the mannerdescribed above. After the organic solvent is removed from the cleaningdrum 112, it can either be discarded or recovered and decontaminated forreuse using solvent recovery systems known in the art. Furthermore,multiple cleaning cycles can be used if desired, with each cleaningcycle using the same organic solvent or different organic solvents. Ifmultiple cleaning cycles are used, each cleaning cycle can occur in thesame cleaning vessel, or a separate cleaning vessel can be used for eachcleaning cycle.

[0045] After a desired amount of the organic solvent is removed from thetextiles by rotating the cleaning drum 112 at high speed, the textilesare moved from the cleaning drum 112 to the drying drum 122 within thedrying vessel 120 in the same manner textiles are moved between machinesin conventional cleaning systems. In an alternate embodiment, a singledrum can be used in both the cleaning cycle and the drying cycle, sothat, rather than transferring the textiles between the cleaning drum112 and the drying drum 122, a single drum containing the textiles istransferred between the cleaning vessel 110 and the drying vessel 120.If the cleaning vessel 110 is pressurized during the cleaning cycle, itmust be depressurized before the textiles are removed. Once the textileshave been placed in the drying drum 122, pressurized fluid solvent, suchas that contained in the carbon dioxide tank 132, is added to the dryingvessel 120 via lines 154 and 155 by opening valve 175, closing valves174 and 176, and activating pump 192 to pump pressurized fluid solventthrough the inlet 124 of the drying vessel 120 via lines 154 and 155.When pressurized fluid solvent is added to the drying vessel 120, theorganic solvent remaining on the textiles dissolves in the pressurizedfluid solvent.

[0046] After a sufficient amount of pressurized fluid solvent is addedso that the desired level of organic solvent has been dissolved, thepressurized fluid solvent and organic solvent combination is removedfrom the drying vessel 120, and therefore also from the drying drum 122,by opening valve 176, closing valve 175 and activating pump 193 to pumpthe pressurized fluid solvent and organic solvent combination throughoutlet 126 via line 156. If desired, this process may be repeated toremove additional organic solvent. The drying drum 122 is then rotatedat a high speed, such as 150-350 rpm, to further remove the pressurizedfluid solvent and organic solvent combination from the textiles. Thedrying drum 122 is preferably perforated so that, when the textiles arerotated in the drying drum 122 at a high speed, the pressurized fluidsolvent and organic solvent combination can drain from the drying drum122. Any pressurized fluid solvent and organic solvent combinationremoved from the textiles by spinning the drying drum 122 at high speedis also pumped from the drying vessel 120 in the manner described above.After the pressurized fluid solvent and organic solvent combination isremoved from the drying vessel 120, it can either be discarded orseparated and recovered for reuse with solvent recovery systems known inthe art. Note that, while preferred, it is not necessary to include ahigh speed spin cycle remove pressurized fluid solvent from thetextiles.

[0047] After a desired amount of the pressurized fluid solvent isremoved from the textiles by rotating the drying drum 122, the dryingvessel 120 is depressurized over a period of about 5-15 minutes. Thedepressurization of the drying vessel 120 vaporizes any remainingpressurized fluid solvent, leaving dry, solvent-free textiles in thedrying drum 122. The pressurized fluid solvent that has been vaporizedis then removed from the drying vessel 120 by opening valve 176, closingvalve 175, and activating pump 193. As a result, the vaporizedpressurized fluid solvent is pumped through the outlet 126, line 156 andvalve 176, where it can then either be vented to the atmosphere orrecovered and recompressed for reuse.

[0048] While the cleaning system 100 has been described as a completesystem, an existing conventional dry cleaning system may be convertedfor use in accordance with the present invention. To convert aconventional dry cleaning system, the organic solvent described above isused to clean textiles in the conventional system. A separatepressurized vessel is added to the conventional system for drying thetextiles with pressurized fluid solvent. Thus, the conventional systemis converted for use with a pressurized fluid solvent. For example, thesystem in FIG. 1 could represent such a converted system, wherein thecomponents of the cleaning machine 102 are conventional, and thepressurized fluid solvent tank 132 is not in communication with thecleaning vessel 100. In such a situation, the drying machine 104 is theadd-on part of the conventional cleaning machine.

[0049] Furthermore, while the system shown in FIG. 1 comprises a singlecleaning vessel, multiple cleaning vessels could be used, so that thetextiles are subjected to multiple cleaning steps, with each cleaningstep carried out in a different cleaning vessel using the same ordifferent organic solvents in each step. The description of the singlecleaning vessel is merely for purposes of description and should not beconstrued as limiting the scope of the invention.

[0050] Referring now to FIG. 2, a block diagram of an alternateembodiment of the present invention, a cleaning system having a singlechamber for cleaning and drying the textiles, is shown. The cleaningsystem 200 generally comprises a cleaning machine having a pressurizablevessel 210. The vessel 210 is operatively connected to, via one or moremotor activated shafts (not shown), a perforated rotatable drum or wheel212 within the vessel 210 with an inlet 214 to the vessel 210 and anoutlet 216 from the vessel 210 through which dry cleaning fluids canpass.

[0051] An organic solvent tank 220 holds any suitable organic solvent,such as those described above, to be introduced to the vessel 210through the inlet 214. A pressurized fluid solvent tank 222 holdspressurized fluid solvent to be added to the vessel 210 through theinlet 214. Filtration assembly 224 contains one or more filters thatcontinuously remove contaminants from the organic solvent from thevessel 210 and drum 212 as cleaning occurs.

[0052] The components of the cleaning system 200 are connected withlines 230-234 that transfer organic solvents and vaporized andpressurized fluid solvent between components of the system. The term“line” as used herein is understood to refer to a piping network orsimilar conduit capable of conveying fluid and, for certain purposes, iscapable of being pressurized. The transfer of the organic solvents andvaporized and pressurized fluid solvent through the lines 230-234 isdirected by valves 250-254 and pumps 240-242. While pumps 240-242 areshown in the described embodiment, any method of transferring liquidand/or vapor between components can be used, such as adding pressure tothe component using a compressor to force the liquid and/or vapor fromthe component.

[0053] The textiles are cleaned with an organic solvent such as thosepreviously described. The textiles may also be cleaned with acombination of organic solvent and pressurized fluid solvent, and thiscombination may be in varying proportions of 50-100% by weight organicsolvent and 0-50% by weight pressurized fluid solvent. In the cleaningprocess, the textiles are first sorted as necessary to place thetextiles into groups suitable to be cleaned together. The textiles maythen be spot treated as necessary to remove any stains that may not beremoved during the cleaning process. The textiles are then placed intothe drum 212 within the vessel 210 of the cleaning system 200. It ispreferred that the drum 212 be perforated to allow for free interchangeof solvent between the drum 212 and the vessel 210 as well as totransport soil from the textiles to the filtration assembly 224.

[0054] After the textiles are placed in the drum 212, an organic solventcontained in the organic solvent tank 220 is added to, the vessel 210via line 231 by opening valve 251, closing valves 250, 252, 253 and 254,and activating pump 242 to pump organic solvent through the inlet 214 ofthe vessel 210. The organic solvent may contain one or more co-solvents,detergents, water, or other additives to enhance the cleaning capabilityof the cleaning system 200. Alternatively, one or more additives may beadded directly to the vessel. Pressurized fluid solvent may also beadded to the vessel 210 along with the organic solvent to enhancecleaning. The pressurized fluid solvent is added to the vessel 210 vialine 230 by opening valve 250, closing valves 251, 252, 253 and 254, andactivating pump 240 to pump the pressurized fluid solvent through theinlet 214 of the vessel 210.

[0055] When the desired amount of the organic solvent, or combination oforganic solvent and pressurized fluid solvent as described above, isadded to the vessel 210, the motor (not shown) is activated and the drum212 is agitated and/or rotated. During this phase, the organic solvent,as well as pressurized fluid solvent if used in combination, iscontinuously cycled through the filtration assembly 224 by openingvalves 252 and 253, closing valves 250, 251 and 254, and activating pump241. Filtration assembly 224 may include one or more fine mesh filtersto remove particulate contaminants from the organic solvent andpressurized fluid solvent passing therethrough and may alternatively orin addition include one or more absorptive or adsorptive filters toremove water, dyes, and other dissolved contaminants from the organicsolvent. Exemplary configurations for filter assemblies that can be usedto remove contaminants from either the organic solvent or thepressurized fluid solvent are described more fully in U.S. applicationSer. No. 08/994,583 incorporated herein by reference. As a result, theorganic solvent is pumped through outlet 216, valve 253, line 233,filter assembly 224, line 232, valve 252 and reenters the vessel 210 viainlet 214. This cycling advantageously removes contaminants, includingparticulate contaminants and/or soluble contaminants, from the organicsolvent and pressurized fluid solvent and reintroduces filtered solventto the vessel 210. Through this process, contaminants are removed fromthe textiles.

[0056] After sufficient time has passed so that the desired level ofcontaminants is removed from the textiles and solvents, the organicsolvent is removed from the vessel 210 and drum 212 by opening valve254, closing valves 250, 251, 252 and 253, and activating pump 241 topump the organic solvent through outlet 216 and line 234. If pressurizedfluid solvent is used in combination with organic solvent, it may benecessary to first separate the pressurized fluid solvent from theorganic solvent. The organic solvent can then either be discarded or,preferably, contaminants may be removed from the organic solvent and theorganic solvent recovered for further use. Contaminants may be removedfrom the organic solvent with solvent recovery systems known in the art.The drum 212 is then rotated at a high speed, such as 400-800 rpm, tofurther remove organic solvent from the textiles. The drum 212 ispreferably perforated so that, when the textiles are rotated in the drum212 at a high speed, the organic solvent can drain from the cleaningdrum 212. Any organic solvent removed from the textiles by rotating thedrum 212 at high speed can also either be discarded or recovered forfurther use.

[0057] After a desired amount of organic solvent is removed from thetextiles by rotating the drum 212, pressurized fluid solvent containedin the pressurized fluid tank 222 is added to the vessel 210 by openingvalve 250, closing valves 251, 252, 253 and 254, and activating pump 240to pump pressurized fluid solvent through the inlet 214 of thepressurizable vessel 210 via line 230. When pressurized fluid solvent isadded to the vessel 210, organic solvent remaining on the textilesdissolves in the pressurized fluid solvent.

[0058] After a sufficient amount of pressurized fluid solvent is addedso that the desired level of organic solvent has been dissolved, thepressurized fluid solvent and organic solvent combination is removedfrom the vessel 210 by opening valve 254, closing valves 250, 251, 252and 253, and activating pump 241 to pump the pressurized fluid solventand organic solvent combination through outlet 216 and line 234. Notethat pump 241 may actually require two pumps, one for pumping the lowpressure organic solvent in the cleaning cycle and one for pumping thepressurized fluid solvent in the drying cycle.

[0059] The pressurized fluid solvent and organic solvent combination canthen either be discarded or the combination may be separated and theorganic solvent and pressurized fluid solvent separately recovered forfurther use. The drum 212 is then rotated at a high speed, such as150-350 rpm to further remove pressurized fluid solvent and organicsolvent combination from the textiles. Any pressurized fluid solvent andorganic solvent combination removed from the textiles by spinning thedrum 212 at high speed can also either be discarded or retained forfurther use. Note that, while preferred, it is not necessary to includea high speed spin cycle to remove pressurized fluid solvent from thetextiles.

[0060] After a desired amount of the pressurized fluid solvent isremoved from the textiles by rotating the drum 212, the vessel 210 isdepressurized over a period of about 5-15 minutes. The depressurizationof the vessel 210 vaporizes the pressurized fluid solvent, leaving dry,solvent-free textiles in the drum 212. The pressurized fluid solventthat has been vaporized is then removed from the vessel 210 by openingvalve 254, closing valves 250, 251, 252 and 253, and activating pump 241to pump the vaporized pressurized fluid solvent through outlet 216 andline 234. Note that while a single pump is shown as pump 241, separatepumps may be necessary to pump organic solvent, pressurized fluidsolvent and pressurized fluid solvent vapors, at pump 241. The remainingvaporized pressurized fluid solvent can then either be vented into theatmosphere or compressed back into pressurized fluid solvent for furtheruse.

[0061] As discussed above, dipropylene glycol n-butyl ether,tripropylene glycol n-butyl ether and tripropylene glycol methyl etherare the preferred organic solvents for use in the present invention, asshown in the test results below. Table 2 shows results of detergencytesting for each of a number of solvents that may be suitable for use inthe present invention. Table 3 shows results of testing of drying andextraction of those solvents using densified carbon dioxide.

[0062] Detergency tests were performed using a number of differentsolvents without detergents, co-solvents, or other additives. Thesolvents selected for testing include organic solvents and liquid carbondioxide. Two aspects of detergency were investigated—soil removal andsoil redeposition. The former refers to the ability of a solvent toremove soil from a substrate while the latter refers to the ability of asolvent to prevent soil from being redeposited on a substrate during thecleaning process. Wascherei Forschungs Institute, Krefeld Germany(“WFK”) standard soiled swatches that have been stained with a range ofinsoluble materials and WFK white cotton swatches, both obtained fromTESTFABRICS, Inc., were used to evaluate soil removal and soilredeposition, respectively.

[0063] Soil removal and redeposition for each solvent was quantifiedusing the Delta Whiteness Index. This method entails measuring theWhiteness Index of each swatch before and after processing. The DeltaWhiteness Index is calculated by subtracting the Whiteness Index of theswatch before processing from the Whiteness Index of the swatch afterprocessing. The Whiteness Index is a function of the light reflectanceof the swatch and in this application is an indication of the amount ofsoil on the swatch. More soil results in a lower light reflectance andWhiteness Index for the swatch. The Whiteness indices were measuredusing a reflectometer manufactured by Hunter Laboratories.

[0064] Organic solvent testing was carried out in a Launder-Ometer whilethe densified carbon dioxide testing was carried out in a Parr Bomb.After measuring their Whiteness Indices, two WFK standard soil swatchesand two WFK white cotton swatches were placed in a Launder-Ometer cupwith 25 stainless steel ball bearings and 150 mL of the solvent ofinterest. The cup was then sealed, placed in the Launder-Ometer andagitated for a specified length of time. Afterwards, the swatches wereremoved and placed in a Parr Bomb equipped with a mesh basket.Approximately 1.5 liters of liquid carbon dioxide between 5° C. and 25°C. and 570 psig and 830 psig was transferred to the Parr Bomb. Afterseveral minutes the Parr Bomb was vented and the dry swatches removedand allowed to reach room temperature. Testing of densified carbondioxide was carried out by placing the swatches in a Parr Bomb,transferring liquid carbon dioxide at 20° C. and 830 psig to the ParrBomb. The swatches were fastened to a, wire frame attached to arotatable shaft to enable the swatches to be agitated while immersed inthe liquid carbon dioxide. The Whiteness Index of the processed swatcheswas determined using the reflectometer. The two Delta Whiteness Indicesobtained for each pair of swatches were averaged. The results arepresented in Table 2.

[0065] Because the Delta Whiteness Index is calculated by subtractingthe Whiteness Index of a swatch before processing from the WhitenessIndex value after processing, a positive Delta Whiteness Index indicatesthat there was an increase in Whiteness Index as a result of processing.In practical terms, this means that soil was removed during processing.In fact, the higher the Delta Whiteness Value, the more soil was removedfrom the swatch during processing. Each of the organic solvents testedexhibited significant soil removal. Densified carbon dioxide alone, onthe other hand, exhibited no soil removal. The WFK white cotton swatchesexhibited a decrease in Delta Whiteness Indices indicating that the soilwas deposited on the swatches during the cleaning process. Therefore, a“less negative” Delta Whiteness Index suggests that less soil wasredeposited. It should be noted that the seemingly excellent resultobtained for densified carbon dioxide is an anomaly and resulted fromthe fact that essentially no soil removal took place and thereforeessentially no soil was present in the solvent which could be depositedon the swatch. The organic solvents on the other hand, exhibited goodsoil redeposition results. TABLE 2 Delta Whiteness Values CleaningInsoluble Insoluble Time Soil Soil Solvent (minutes) RemovalRedeposition Densified Carbon Dioxide 20 0.00 −0.54 (at 20° C. and 830psig) Ethylene Glycol Ethyl Ether 12 13.87 −5.10 Ethylene Glycol EthylEther 12 16.10 −11.40 Acetate Diethylene Glycol Butyl Ether 12 12.80−5.11 Propylene Glycol t-butyl Ether 12 14.35 −13.50 Dipropylene GlycolMethyl Ether 20 11.84 −5.64 Tripropylene Glycol Methyl Ether 12 13.48−5.60 Dipropylene Glycol n-Butyl Ether 12 13.97 −6.22 Dipropylene Glycoln-Propyl Ether 12 13.15 −7.50 Tripropylene Glycol n-Butyl Ether 12 13.24−4.35

[0066] To evaluate the ability of densified carbon dioxide to extractorganic solvent from a substrate, WFK white cotton swatches were used.One swatch was weighed dry and then immersed in an organic solventsample. Excess solvent was removed from the swatch using a ringermanufactured by Atlas Electric Devices Company. The damp swatch wasre-weighed to determine the amount of solvent retained in the fabric.After placing the damp swatch in a Parr Bomb densified carbon dioxidewas transferred to the Parr Bomb. The temperature and pressure of thedensified carbon dioxide for all of the trials ranged from 5° C. to 20°C. and from 570 psig-830 psig. After five minutes the Parr Bomb wasvented and the swatch removed. The swatch was next subjected to Soxhletextraction using methylene chloride for a minimum of two hours. Thisapparatus enables the swatch to be continuously extracted to remove theorganic solvent from the swatch. After determining the concentration ofthe organic solvent in the extract using gas chromatography, the amountof organic solvent remaining on the swatch after exposure to densifiedcarbon dioxide was calculated by multiplying the concentration of theorganic solvent in the extract by the volume of the extract. A differentswatch was used for each of the tests. The results of these tests areincluded in Table 3. As the results indicate, the extraction processusing densified carbon dioxide is extremely effective. TABLE 3 Weight ofPercentage Weight of Densified by Weight of Solvent on Test CarbonSolvent Swatch (grams) Dioxide Removed Before After Used from SolventExtraction Extraction (kilograms) Swatch Ethylene Glycol 1.8718 0.00691.35 99.63 Ethyl Ether Ethylene Glycol 1.9017 0.0002 1.48 99.99 EthylEther Acetate Diethylene Glycol 1.9548 0.0033 1.72 99.83 Butyl EtherPropylene Glycol 2.0927 0.0010 1.24 99.95 t-butyl Ether DipropyleneGlycol 2.1209 0.0005 1.31 99.98 Methyl Ether Tripropylene Glycol 1.99100.0022 1.71 99.89 Methyl Ether Dipropylene Glycol 1.8005 0.0023 1.7799.87 n-Butyl Ether Dipropylene Glycol 1.7096 0.0034 1.59 99.80 n-ButylEther Dipropylene Glycol 1.7651 0.0018 3.36 99.90 n-Butyl EtherDipropylene Glycol 1.7958 0.0012 1.48 99.94 n-Propyl Ether TripropyleneGlycol 1.8670 0.0034 1.30 99.82 n-Butyl Ether

[0067] It is to be understood that a wide range of changes andmodifications to the embodiments described above will be apparent tothose skilled in the art and are contemplated. It is, therefore,intended that the foregoing detailed description be regarded asillustrative rather than limiting, and that it be understood that it isthe following claims, including all equivalents, that are intended todefine the spirit and scope of the invention.

What is claimed is:
 1. A process for cleaning substrates comprising:placing the substrates to be cleaned in a cleaning vessel; addingorganic solvent to the cleaning vessel; cleaning the substrates with theorganic solvent; removing a portion of the organic solvent from thecleaning vessel; placing the substrates in a drying vessel; addingpressurized fluid solvent to the drying vessel; removing the pressurizedfluid solvent from the drying vessel; and removing the substrates fromthe drying vessel.
 2. The process of claim 1 wherein the substratesbeing cleaned comprise textiles.
 3. The process of claim 2 wherein thecleaning vessel further contains a rotatable drum within the cleaningvessel into which the textiles are placed.
 4. The process of claim 3wherein removing a portion of the organic solvent from the cleaningvessel further comprises rotating the drum at sufficient speed toextract the portion of the organic solvent from the textiles.
 5. Theprocess of claim 2 wherein removing the pressurized fluid solvent fromthe drying vessel further comprises the step of depressurizing thedrying vessel to vaporize at least a portion of the pressurized fluidsolvent.
 6. The process of claim 5 wherein the drying vessel furthercomprises a rotatable drum within the drying vessel into which thetextiles are placed.
 7. The process of claim 6 wherein removing thepressurized fluid solvent from the drying vessel further comprises thestep of rotating the drum at sufficient speed to extract a portion ofthe pressurized fluid solvent from the textiles before the drying vesselis depressurized.
 8. The process of claim 1 wherein the organic solvent:is soluble in carbon dioxide between 600 and 1050 pounds per square inchand between 5 and 30 degrees Celsius; has an evaporation rate of lowerthan 30 (based on n-butyl acetate=100); has a dispersion Hansensolubility parameter of between 7.2 (cal/cm³)^(1/2) and 8.1(cal/cm³)^(1/2); has a polar Hansen solubility parameter of between 2.0(cal/cm³)^(1/2) and 4.8 (cal/cm³)^(1/2); and has a hydrogen bondingHansen solubility parameter of between 4.0 (cal/cm³)^(1/2) and 7.3(cal/cm³)^(1/2).
 9. The process of claim 8 wherein the organic solventfurther: has a specific gravity of greater than 0.7; and has a flashpoint greater than 200 degrees Fahrenheit.
 10. The process of claim 9wherein the pressurized fluid solvent is densified carbon dioxide. 11.The process of claim 1 wherein the organic solvent is a glycol ether.12. The process of claim 1 wherein the organic solvent is a poly glycolether.
 13. The process of claim 1 wherein the organic solvent isselected from a group including dipropylene glycol n-butyl ether,tripropylene glycol n-butyl ether, tripropylene glycol methyl ether, andmixtures thereof.
 14. The process of claim 1 wherein the organic solventcomprises a combination of organic solvent and pressurized fluidsolvent.
 15. A process for cleaning substrates comprising: placing thesubstrates to be cleaned in a vessel; adding organic solvent to thevessel; cleaning the substrates with the organic solvent; removing aportion of the organic solvent from the vessel; adding pressurized-fluidsolvent to the vessel; removing the pressurized fluid solvent from thevessel; and removing the substrates from the vessel.
 16. The process ofclaim 15 wherein the substrates being cleaned comprise textiles.
 17. Theprocess of claim 15 wherein the vessel further contains a rotatable drumwithin the vessel into which the textiles are placed.
 18. The process ofclaim 17 wherein removing a portion of the organic solvent from thevessel further comprises rotating the drum at sufficient speed toextract the portion of the organic solvent from the textiles.
 19. Theprocess of claim 17 wherein removing a portion of the pressurized fluidsolvent from the vessel further comprises the step of depressurizing thevessel to vaporize the remaining pressurized fluid solvent.
 20. Theprocess of claim 19 wherein removing a portion of the pressurized fluidsolvent from the vessel further comprises the step of rotating the drumat sufficient speed to extract a portion of the pressurized fluidsolvent from the textiles before the vessel is depressurized.
 21. Theprocess of claim 15 wherein the organic solvent: is soluble in carbondioxide between 600 and 1050 pounds per square inch and between 5 and 30degrees Celsius; has an evaporation rate of lower than 30 (based onn-butyl acetate=100); has a dispersion Hansen solubility parameter ofbetween 7.2 (cal/cm³)^(1/2) and 8.1 (cal/cm³)^(1/2); has a polar Hansensolubility parameter of between 2.0 (cal/cm³)^(1/2) and 4.8(cal/cm³)^(1/2); and has a hydrogen bonding Hansen solubility parameterof between 4.0 (cal/cm³)^(1/2) and 7.3 (cal/cm³)^(1/2).
 22. The processof claim 21 wherein the organic solvent further: has a specific gravityof greater than 0.7; and has a flash point greater than 200 degreesFahrenheit.
 23. The process of claim 22 wherein the pressurized fluidsolvent is densified carbon dioxide.
 24. The process of claim 15 whereinthe organic solvent is a glycol ether.
 25. The process of claim 15wherein the organic solvent is a poly glycol ether.
 26. The process ofclaim 15 wherein the organic solvent is selected from a group includingdipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether,tripropylene glycol methyl ether, and mixtures thereof.
 27. The processof claim 13 wherein the organic solvent comprises a combination oforganic solvent and pressurized fluid solvent.
 28. A process forcleaning textiles comprising: placing the textiles to be cleaned into acleaning drum within a cleaning vessel; adding organic solvent to thecleaning vessel; cleaning the textiles with the organic solvent;removing a portion of the organic solvent from the cleaning vessel;rotating the cleaning drum to extract a portion of the organic solventfrom the textiles; placing the textiles into a drying drum within apressurizable drying vessel; adding pressurized fluid solvent to thedrying vessel; removing a portion of the pressurized fluid solvent fromthe drying vessel; rotating the drying drum to extract a portion of thepressurized fluid solvent from the textiles; depressurizing the dryingvessel to remove the remainder of the carbon dioxide by evaporation; andremoving the textiles from the drying drum.
 29. A system for cleaningsubstrates comprising: a cleaning vessel adapted to hold contaminatedsubstrates and organic solvent; an organic solvent tank operativelyconnected to the cleaning vessel; a pump for pumping organic solventfrom the organic solvent tank to the cleaning vessel; a drying vesseladapted to hold cleaned substrates and pressurized fluid solvent; acarbon dioxide tank operatively connected to the drying vessel; and apump for pumping pressurized fluid solvent from the carbon dioxide tankto the drying vessel.
 30. The system of claim 29 wherein the substratescomprise textiles.
 31. The system of claim 30 wherein the cleaningvessel further comprises a rotatable drum within the cleaning vesseladapted to hold textiles.
 32. The system of claim 31 wherein therotatable drum is adapted to rotate at sufficient speed to extract aportion of the organic solvent from the textiles.
 33. The system ofclaim 30 wherein the drying vessel further comprises a rotatable drumwithin the drying vessel adapted to hold textiles.
 34. The system ofclaim 33 wherein the rotatable drum is adapted to rotate at sufficientspeed to extract a portion of the pressurized fluid solvent from thetextiles.
 35. The system of claim 29 wherein the organic solvent: issoluble in carbon dioxide between 600 and 1050 pounds per square inchand between 5 and 30 degrees Celsius; has an evaporation rate of lowerthan 30 (based-on n-butyl acetate=100); has a dispersion Hansensolubility parameter of between 7.2 (cal/cm³)^(1/2) and 8.1(cal/cm³)^(1/2); has a polar Hansen solubility parameter of between 2.0(cal/cm³)^(1/2) and 4.8 (cal/cm³)^(1/2); and has a hydrogen bondingHansen solubility parameter of between 4.0 (cal/cm³)^(1/2) and 7.3(cal/cm³)^(1/2).
 36. The system of claim 35 wherein the organic solventfurther: has a specific gravity of greater than 0.7; and has a flashpoint greater than 200 degrees Fahrenheit.
 37. The system of claim 36wherein the pressurized fluid solvent is densified carbon dioxide. 38.The system of claim 29 wherein the organic solvent is a glycol ether.39. The system of claim 29 wherein the organic solvent is a poly glycolether.
 40. The system of claim 29 wherein the organic solvent isselected from a group including dipropylene glycol n-butyl ether,tripropylene glycol n-butyl ether, tripropylene glycol methyl ether, andmixtures thereof.
 41. A system for cleaning substrates comprising: avessel adapted to hold substrates, organic solvent, and pressurizedfluid solvent; an organic solvent tank operatively connected to thevessel; a pump for pumping organic solvent from the organic solvent tankto the vessel; a pressurized fluid solvent tank operatively connected tothe vessel; and a pump for pumping pressurized fluid solvent from thepressurized fluid solvent tank to the vessel.
 42. The system of claim 41wherein the substrates comprise textiles.
 43. The system of claim 42wherein the vessel further comprises a rotatable drum within the vesseladapted to hold textiles.
 44. The system of claim 43 wherein therotatable drum is adapted to rotate at sufficient speed to extract aportion of the organic solvent and a portion of the pressurized fluidsolvent from the textiles.
 45. The system of claim 41 wherein theorganic solvent: is soluble in carbon dioxide between 600 and 1050pounds per square inch and between 5 and 30 degrees Celsius; has anevaporation rate of lower than 30 (based on n-butyl acetate=100); has adispersion Hansen solubility parameter of between 7.2 (cal/cm³)^(1/2)and 8.1 (cal/cm³)^(1/2); has a polar Hansen solubility parameter ofbetween 2.0 (cal/cm³)^(1/2) and 4.8 (cal/cm³)^(1/2); and has a hydrogenbonding Hansen solubility parameter of between 4.0 (cal/cm³)^(1/2) and7.3 (cal/cm³)^(1/2).
 46. The system of claim 45 wherein the organicsolvent further: has a specific gravity of greater than 0.7; and has aflash point greater than 200 degrees Fahrenheit.
 47. The system of claim46 wherein the pressurized fluid solvent is densified carbon dioxide.48. The system of claim 41 wherein the organic solvent is a glycolether.
 49. The system of claim 41 wherein the organic solvent is a polyglycol ether.
 50. The system of claim 41 wherein the organic solvent isselected from a group including dipropylene glycol n-butyl ether,tripropylene glycol n-butyl ether, tripropylene glycol methyl ether andmixtures thereof.
 51. A system for cleaning textiles comprising: acleaning vessel adapted to retain textiles and organic solvent and ableto agitate the textiles and the organic solvent; an organic solvent tankoperatively connected to the cleaning vessel; a drying vessel adapted toretain textiles and pressurized fluid solvent and able to agitate thetextiles and the pressurized fluid solvent; and a pressurized fluidsolvent tank operatively connected to the drying vessel.
 52. A systemfor cleaning textiles comprising: a pressurizable vessel adapted toretain textiles and organic solvent and pressurized fluid solvent andable to agitate the textiles and the organic solvent and the pressurizedfluid solvent; an organic solvent tank operatively connected to thepressurizable vessel; and a pressurized fluid solvent tank operativelyconnected to the pressurizable vessel.
 53. A system for cleaningsubstrates comprising a cleaning vessel adapted to hold contaminatedsubstrates and organic solvent; an organic solvent tank operativelyconnected to the cleaning vessel and containing organic solvent; meansfor moving organic solvent from the organic solvent tank to the cleaningvessel; a drying vessel adapted to hold cleaned substrates andpressurized fluid solvent; a pressurized fluid solvent tank operativelyconnected to the drying vessel and containing pressurized fluid solvent;and means for moving pressurized fluid solvent from the pressurizedfluid solvent tank to the drying vessel.
 54. The system of claim 53wherein the substrates comprise textiles.
 55. The system of claim 54wherein the cleaning vessel further comprises an agitation means foragitating the cleaning vessel adapted to hold textiles and the organicsolvent.
 56. The system of claim 55 wherein the agitation means isadapted to agitate the cleaning vessel to extract a portion of theorganic solvent from the textiles.
 57. The system of claim 54 whereinthe cleaning vessel is adapted to depressurize so as to vaporize atleast a portion of the pressurized fluid solvent.
 58. The system ofclaim 53 wherein the organic solvent: is soluble in carbon dioxidebetween 600 and 1050 pounds per square inch and between 5 and 30 degreesCelsius;. has an evaporation rate of lower than 30 (based on n-butylacetate=100); has a dispersion Hansen solubility parameter of between7.2 (cal/cm³)^(1/2) and 8.1 (cal/cm³)^(1/2); has a polar Hansensolubility parameter of between 2.0 (cal/cm³)^(1/2) and 4.8(cal/cm³)^(1/2); and has a hydrogen bonding Hansen solubility parameterof between 4.0 (cal/cm³)^(1/2) and 7.3 (cal/cm³)^(1/2).
 59. The systemof claim 58 wherein the organic solvent further: has a specific gravityof greater than 0.7; and has a flash point greater than 200 degreesFahrenheit.
 60. The system of claim 59 wherein the pressurized fluidsolvent is densified carbon dioxide.